Curing bag



July 1949- c. N. SPENCER 2,476,831

I N v a n TO R COQWIH H.5PEHCEQ Patented July 19, 1949 CURING BAG CorwinN. Spencer, Akron, Ohio, assignor to The Firestone Tire & RubberCompany, Akron, Ohio, a corporation of Ohio Application December 13,1946, Serial No. 716,017

3 Claims. 1

This invention relates to a curing bag and more especially to aninflatable full circle curing bag composed of rubber, or rubber-likematerial, of the type commonly used in providing internal pressure forpneumatic vehicle tires during their vulcanization.

A principal object of the invention is to provide a curing bag of thecharacter described provided with means for the prevention of trappingair between the curing bag and a tire.

Another object of the present invention is to provide means upon theexternal surface of a curing bag adapted to vent air to the atmospherefrom between the curing bag and a tire in which said bag is used in atire vulcanizing operation.

A further object of the present invention is to provide air ventingmeans upon the outer surface of a curing bag of a type that will notinjure a tire in which the bag is used.

With these and other objects in view, which will appear as thedescription proceeds, the invention resides in the feature ofconstruction, combination and arrangement of parts as will behereinafter more fully described in detail, illustrated in theaccompanying drawing, which discloses the preferred embodiment of theinvention, and pointed out in the claims hereunto appended.

In the accompanying drawing:

Fig. 1 is a perspective view or a curing bag embodying the presentinvention;

Fig. 2 is a fragmentary sectional view taken on line 22 of Fig. 1 butdrawn on an enlarged scale;

Fig. 3 is a sectional view taken on line 3-3 of Fig. 1;

Fig. 4 is a partial sectional view on an enlarged scale illustrating therelative position of a curing bag, a tire and a tire curing mold duringa tire vulcanization; and

Fig. 5 is a fragmentary sectional view taken on I line 5-5 of Fig. 4illustrating the relative position of the vents of the curing bag andthe inside wall of a tire just before the curing bag has molded theinside of the tire into its final molded shape.

A common and troublesome manufacturing defect of large pneumatic cordtires such as, for example, size 1100-24, is a large sidewall or treadblister in the form of a separation, which defect becomes discernible atthe time, or shortly after, a tire is removed from its curing mold.Prior to the present invention many expedients were tried to preventthese costly defects, but without avail. For example, tire builders wererequired to practice great care to avoid trapping air between the rubberof the tread and sidewall and the fabric body of the tire. Also specialcements were used to obtain improved unions between the sidewalls,treads and the fabric tire bodies. Another expedient practiced was topunch small holes through the rubber sidewall and treads to let thegases escape, whereby avoidance of a blister, or separation was sought.Improved compounds, and numerous other ways and means, were tried butnone was effective in avoiding the said blistering, or separation.

Applicant discovered that the blisters resulted from air trapped notbetween the fabric body and its rubber covering, but between the curingbag and unvulcanized tire. Further that this trapped air worked its waythrough the fabric body of the tire, under the urge of the internalcuring pressure of the bag, until the air reached the sidewall, or treadof the tire. Since the Sid..- wall and tread of the tire are composed ofrubber, which is substantially impervious to air, the said air becomestrapped under pressure against the said sidewall or tread. Applicantdiscovered that when a tire with air so trapped, was removed from a hotmold that the trapped air, under pressure, blew the rubber away from thebody of the tire forming large sidewall, or tread blisters according tothe location of the said blisters. Applicant conceived the idea ofpreventing such air traps, and thereby the blisters, by utilizing acombination of small ribs on the base and sides of the curing bag, andin combination therewith a series of narrow grooves cut in the base ofthe tire mold cavity. Said grooves extend from the bead seat portion ofsaid mold cavity to the inside parting line of the tire mold, saidgrooves continuing radially inwardly along the sides of said partingline to the open inside center of the mold.

Referring to the drawing in detail, particularly to Figs. 1 and 2, itwill be seen that circumferentially spaced ribs ll extend around thebase of a curing bag In and radially up the sides thereof to a positionjust beyond the widest point of the bag. While the shape and size ofribs ll may be changed, a rib 1 5' inch wide, inch high with a roundedtop has been found to be satisfactory for 1100-24 pneumatic tires whenthe ribs are spaced circumferentially of the bag approxi- -mately onefoot apart.

Referring now particularly to Fig. 4 it will be seen that a tire curingmold I! has a vent groove 20 which extends across the base of the tiremold cavity from a point which falls at the toe of the head of a tire ofthe size and type for which the mold is made. Said groove 20 alsoextends to the mold dividing line 22 and thence radially inwardly alongthe sides of said dividing line to the open 3 center of the mold. Thevent grooves 20 are similarly placed in both halves of the tire mold, aplurality of such grooves being circumferentially spaced about the baseof said mold. It has been found that a spacing of approximately eight 5the separation defects described herelnahmlezassw;

will now be explained.

The general practice in ,inolding,and..,vu1caniz=- ing a pneumatic cordtire i's'to use a curingbag as a means for pressing the tire against:its'molditl The curing bag is in the form of an endless tubeandl.-is-.;placed-.in-.;the tine by :an. operatiom commonly, reierredto.- in-,the-.-ar.tt.as a-:tire;bagging operation. The. bagged..- tire.is..usua11y, laid; directly. in a. vulcanizing- -mold;. which isthe casein the. embodiment, oil. the, invention. illustrated. Howeveranother-method;.;in common-mse is, to mount.the.-..bagg,ech tire. oncuring; ring; and. then layatheeassembledtire bagandouring rings inrthetire mold. The curing rings are alsoq-reierrodlto int-the. art..,asrbeadfonmingmings-on simple formins; rin s. lit-is,to.-.be.-:understood.,that it curing rings. are used: that.-, grooves.corresponding, to groov 0. inmold l Lareatoebeecut. imthecuring rin s-Thebag: I 01 illustrated isprovided withganinlet; and .outletstem -lLthr-ough whiclratfluid-pressure medium flows to.andfr0m thezbagl.Irrthaevent that, circulating; water is used. as.- a pressure mediumbag. "I may beeprovidedi withanc: inlet andl an outlet stem,aswillfloeunderstoodl-bxthose;

, familiar. with;.,the,- art.

. Inr the. -vulcanizing-.-operation, theI tirea-Zl ,..with thee-bag.lmmountediherein islaid in moldt2 and the mold l2: is -closed...Internal DIESSUIIfiiiS h1Ii1lZ up in. the, bag.= to through the. medlunrf, air,-.,an; mangoes-water, steam; or .thellike, under pressure flowingthroughstem. Mintosaid bag; Beforerthe internal pressure: is; built; upin: .theebagf; it. fits looselyr. in-the.stire..-permittingconsiderable;air

spacetbetweem thebag andtirez. As internal pressure buflds-upinlthe bagand.the.-expandin.g bag presses its. outer surfaceeagainstitheinsiderotthe tire, anctthe tire vagainst.theetire.fmolcl, mostlofthealrbetweenthe ba randthe tire will normally escape. Howeren. as-'explained, hereinbefora. some of the. air often. becomes trapped:between thelbag and the tires, Thepresentinventionnkents this.trapped-air out'tot the mold: from between the bag and the; tireand outet-the.- tires mold.

Whenthe outer, surfiace: 0t. I 0; presses against. insidesurfaceoi a;tiretthe; ribsa H. cause a slightbridging,ofitheqtire oversaidribs-forming smallrventholeseitl- (see: Fig.- 5.) along-the extent oiisaid ribss The-ribs ll cross theubasewofcbag H1; however. saidbase.contactsthev metalemold.

andthe .ribson the. base aresubstan-tiallyflattened after the bag hasbeen intserviceefor a considerable time. This causes, the-ribs to: losetheir. efileotiveness in iorming saidvent;holesbe,-

4 tween the tire mold and the base of the bag. To insure the movement ofair from between the bag and the tire, the grooves 20 are provided. Thusas pressure is built up in the bag I0, the entrapped air follows thevents 24 to the corner of the base of the bag and there enters grooves29 through which grooves the air flows to the inside parting line. (mthemold. and thence-out of, the mold to thez-afimespherer While theforegoing specification sets forth the invention in specific terms, itis to be understood that numerous changes in shape, size and materialmay be resorted to withoutdeparting from theusp iritl of, thepresentinvention as claimed nereinaiter...

What; lsgclaimedl is:

1. In combination, a tire curing bag, and a tire mcld; said curing baghaving vent ribs integrahtherewith which extend across the base of saidbag and radially outwardly on the outer surface. cttheobag, topointsatleasthalr ofthedistanoesfizom the, base to ,.the.,oro.wn. of. thebag,saidi moldhaving auplurality, of. vent, grooves circlnniferentiallx,spaced about the. axially extendinggbeadlportlonoia tire cavity ofsaidrnoldsaid grooves extending from approximately the point the bead,toe, on a tire .JCUJLBLL in. said. mold comes to.themoliiisrinsideparting, line. andthence, radially, inwardly along. saidparting. line.to the open center ofsaid mold'r. I

21'Inloombination...a,curing. bag, and. atire mold;,Saimcuringbaghaving, re'tisedribs. onthe suriace'zof'its sidewalhsaidgmold having,vent grooves, in. ,the. axially extending head, portion. ofatire.cavitytoiisaidmold; said ribs and grooves extendingtoa common zoneoisaid combination thereby, providin vent, means, f.or. air. from..-be,- tween said tire andscurin 3; In combination, a vented tire moldand. our- ,ing bag,adaptedto.efecttheescape of. air trapped between,.the curing,:bag,and. apneumatic tire d'uringa tirelmolding operation,said vents comprising ribs-@ontheouter surface. of and integralwitli'rsaid; curing bag-said. ribs extending downwardly from they sidesof said. bag to the base nprfiomthereot. and groovesin. the. axiallyextendingbeadpportion oithe'tire cavity of said moldin whichsaidiouringoperation isperformed, saidhgrooves extending iromthe insideparting line ofsaid moldlaterally towardv the sidesot saidmold-.cavity,. whereby said, trapped air escapes along,-.the.sidesoflsaidribstto-that region of the mold provided withcsaid grooves andthrough said grooves to said parting line of said mold, and

-,th.ence,.along,.thel,sides of. the. mold, facing; said.ThQxfQH'QTWlHgKIGfBIBIICES are of record in the file ci f thiapatentrUNITED STATES PATENTS Number Name Date 1,019,506. McGool Mar. 5, 191-21,604,450. Krusemark Oct. 26, 1926 1g98O 55 Z Aevery" r N0v-.'1;3, 19342;0A11-,53t- Eger' May 19, 1936 2956;805? Peacock V May-22, 1945

